WordNet sense 1 (too obvious to be doubted):

indubitable

WordNet sense 2 (not counterfeit or copied):

authentic, bona fide, veritable

WordNet sense 3 (not fake or counterfeit):

echt, genuine

WordNet sense 4 (admitting of no doubt or misunderstanding; having only one meaning or interpretation and leading to only one conclusion):

unambiguous, unequivocal, univocal